


Teach a Dog New Tricks

by ideation



Category: Shingeki no Kyojin | Attack on Titan
Genre: 69 (Sex Position), Alternate Universe - College/University, Alternate Universe - Modern Setting, Anal Sex, First Time, Kink Meme, Loss of Virginity, M/M, Oral Sex, Reiner teaches Eren how to sex okay, Riding, porn with a slight hint of plot
Language: English
Status: Completed
Published: 2013-11-22
Updated: 2014-02-23
Packaged: 2018-01-02 07:51:03
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 5,803
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1054303
Author URL: https://archiveofourown.org/users/ideation/pseuds/ideation
Summary: <blockquote class="userstuff">
              <p>College AU.  Eren doesn't see what all the fuss is about sex.  Reiner aims to correct this.</p><p>Rating will increase to E as of Chapter Two.</p>
            </blockquote>





	1. virgin in a shirt

**Author's Note:**

> Oh man oh man so I really love Reiner/Eren (and Reiner/Eren/Bertholdt, but that's another story) and when I saw a prompt on the kink meme for them (which is also where I got the title from) I could not resist.

“Here’s a towel and some dry clothes,” says Reiner, laying a messily folded pile of cloth on the fake-granite counter.  The bathroom is filled up with steam, and from behind the garishly decorated shower curtain (“They’re called Titans, I think they’re kind of cute,” Bertholdt had said pitifully) he can hear Eren drop a shampoo bottle on his foot.

“Christ--Sorry, thanks, Reiner.  Sorry for imposing like this.  I can’t believe I got caught in the rain like an idiot.”

“Hey, it’s no big deal.  At least you were already coming here rather than wandering around aimlessly,” Reiner laughs.  “What do you want to drink when you get outta there?  Tea, coffee, cocoa?”

“Cocoa!”  For all of Eren’s bravado and tough-guy projections, he’s never hidden his rabid love of sweets from Reiner.  It’s kind of cute.

Eren is kind of cute, he thinks, traitorously and not for the first time, as he boils milk in a saucepan.  He’s known Eren since they were kids, when Eren had moved next door the year Reiner turned fourteen.  Eren was a scrawny, bad-tempered pre-teen who had, for whatever reason, instantly latched onto Reiner like a leech.  Not that he’d minded very much -- Reiner had always been a big-brotherly type -- but it put him into a precarious position once puberty passed them both by.  There was nothing brotherly about how he’d caught himself looking at Eren during the hot summer months when the A/C had been broken and they’d lain sprawled on the floor in a sweaty, bare-chested heap.  Nothing brotherly about how he leaned too close while helping Eren with his Algebra homework,  and certainly nothing brotherly about his near constant dreams starring Eren and himself and very little, if any, clothing.

Reiner sets two steaming mugs on the coffee table and flops onto the couch, sighing and pinching the bridge of his nose.  He can see Eren’s backpack out of the corner of his eye, emptied of textbooks and folders and sitting in a sad heap on the floor.  He’s  been tutoring Eren since high school, and now that they’re in college things haven’t changed.  Eren is still horrible at math and science, Armin is too far advanced to teach him in a way he can understand, and Reiner still can’t say no to him.

“Where’s Bertl?  Out on another date with Annie?”

“Yeah, he--” Reiner looks in the direction of the bathroom and chokes on his own saliva.

Eren is wearing Reiner’s shirt.  Which is logical, considering that it’s what Reiner had left on the counter for him.  What isn’t logical is Reiner forgetting he’s much taller and broader than Eren and not realizing ahead of time just how that shirt is going to hang off of Eren’s shoulder, or how much of Eren’s bare legs will be showing and how easy it is to pretend he isn’t wearing underwear--

Reiner’s so screwed.  Eren looks at him quizzically and he clears his throat, grinning casually.

“Sorry, got a tickle in my throat.  Yeah, he’s taking her out to that new movie she’s been vehemently denying she wants to see.  And then he’ll probably get bullied into doing something else afterwards, like usual.  How their relationship works I’ll never know.”

Eren laughs and plops down next to Reiner on the couch, snagging the mug with a snarling, shaggy-haired monster on it (“It’s called the Rogue Titan, isn’t it cool-looking?” Bertholdt had said anxiously) and taking a preliminary sip of the hot chocolate.

“It tastes better than when Mikasa makes it,” he says, and Reiner chuckles.

“I’ve told you before, that’s because I make it with milk instead of water,” he replies, picking up his own cup (“That’s the Armoured Titan, don’t you think he looks kind of like you?” Bertholdt had said, looking like a puppy expecting to be scolded) and blowing on it cautiously.

“What are you, some kind of cocoa snob?” Eren teases, and it’s only the mugs of hot liquid in their hands that prevents Reiner from shoving Eren onto the floor in retaliation.

“Hey, if you wanna keep drinking the watery crap Mikasa gives you--”

“No no, this is fine,” backtracks Eren hastily, cradling the cup in his hands as though Reiner might take it away, but he’s smiling, and his damnably long legs are tucked up against his chest and Reiner’s shirt is hitched up dangerously around his thighs because of it and--

“Christ, Eren, are you trying to look that sexy on purpose?”

Eren coughs violently and sputters, nearly dropping his mug.  Reiner’s grin is still frozen in place as he thumps Eren on the back, barely hearing himself laughing and asking if the boy is all right over the drumroll of his heart.

_I fucked up.  I fucked up.  Oh god, I fucked up so bad, keep cool Reiner, laugh it off, I fucked up--_

“S-sexy?” Eren says hoarsely, and his face is so red that Reiner half expects him to start steaming.  “Reiner, you idiot, you can’t just say things like that out of the blue--”

“How can I not?  It’s practically a universal truth that wearing someone else’s shirt makes you ten times sexier.  Especially if it’s as big as mine is on you,” says Reiner, smirking easily.  Eren seems to notice for the first time just how much skin he’s exposing and hastily pulls the hem of the shirt over his legs.  “C’mon, Eren, I’m just messing with you.  Do you always act like a blushing virgin when people call you sexy?”  Forget drums, Reiner’s heart is a goddamn jackhammer.

“So what if I am!” says Eren loudly.  “It’s not that weird, okay?  I just never had an interest in things like that, I…”  He trails off at the confused look on Reiner’s face.

“I was kidding, Eren,” Reiner says gently.  “Are you saying that you’re really…?”

“Yeah, I’m a virgin,” mumbles Eren, refusing to look at anything except his knees.

“But you dated Armin for a while, didn’t you?”

“Only a couple of months,” says Eren uncertainly.  “And we didn’t really do anything except kiss a little.  I never-- I don’t know, I didn’t know what to do, and I didn’t think it was that important, anyway.  Armin never said anything about it so I just...I just figured that he didn’t mind either.”  Eren’s eyes widen almost comically.  “You don’t think...is that why he broke up with me?  Because we didn’t--”

“Woah, woah.  Slow your roll, Eren,” says Reiner, and he rubs Eren’s back soothingly.  “Don’t be a dumbass.  You think Armin of all people would break up with you over something like that?”

Eren’s scraggly eyebrows furrow as the rational part of his brain finally catches up with the rest.  “Well...no.  No, he wouldn’t.  Not without telling me, anyway.  He’s never been afraid to call me out on things.”

“Well, there you go, then.”  Reiner’s heart is starting to settle into a less life-threatening rhythm now, and he thinks that, maybe, just maybe, he might be in the clear.  He picks up his forgotten mug of chocolate and takes a big gulp, but the taste is dulled by the nervousness still coating his tastebuds.  Out of the corner of his eye, he can see Eren still huddled in on himself, the fabric of his shirt stretching just enough to allow Reiner to see the faint shapes of Eren’s legs.  He hasn’t stopped frowning, but when Eren turns to look at Reiner, the look in his eyes is inquisitive rather than angry or confused.

“So you’ve done all that stuff, huh?”

“Yeah, I have,” says Reiner, chuckling a little too forcibly and setting down his mug.  “Me and Bertl used to fool around a lot before he got together with Annie, you know.  And before that I had people I dated and messed around with.  Not necessarily at the same time, mind you.”

Eren looks as if all of the secrets of the universe are being slowly revealed to him.  “And it’s fun?”

Reiner doesn’t know if he should laugh or cry at the hopelessly juvenile way that Eren is phrasing that particular question.  When he said he was a virgin, he really did mean virgin.  “I’m not sure if fun is the right word for it,” he says with a grin.  “But it feels damn good.  Like jerking off, but a thousand times better than that.”

Eren’s cheeks turn pink and he squirms self-consciously in his seat.  “I never really thought sex was all that big a deal, is all,” he repeats lamely, biting at his thumbnail.  “Since I could take care of things like that by myself.”

He looks so uncertain, so damnably cute curled up in that god-forsaken shirt that Reiner decides to throw caution to the winds.  Cue the heart palpitations and the the accompanying death rattle of the rest of his common sense.

Reiner leans in close and breathes what is simultaneously the best and worst idea ever into Eren’s ear.  “How about I show you just how good it can be?”

\------------  



	2. the scientific term is horizontal tango

**Summary for the Chapter:**

> College AU. Eren doesn't see what all the fuss is about sex. Reiner aims to correct this.
> 
> Rated E for frickle frackling

**Notes for the Chapter:**

> dear lord this took forever I'm so sorry, I had the most horrible writer's block
> 
> but here it is
> 
> pure self-indulgent smut

Reiner is a bit worried, because Eren’s eyes look as though they’re about to pop right out of his skull.  

“Show...Reiner, you…that’s not funny, you know,” he finally chokes out, and there are so many expressions vying for dominance on his face that Reiner isn't sure of the best way to respond.  

“How’s that me trying to be funny?  I’m 100% serious.  Unless you’re saving your virginity for something…?”

“That’s dumb,” says Eren, and he must realize how harsh it comes out because he immediately opens his mouth again.  “I mean about saving myself, would I do that if I thought sex was no big deal?”

“Fair enough,” replies Reiner with a laugh.  “So how about it?  Might wanna know what you’re doing before you start dating someone, huh?”

Eren squirms again, seemingly weighing his options, and nods once.  Just once.  “Yeah...okay.  Okay, let’s do this.”  He looks so determined that Reiner almost bursts out laughing.

“Relax, soldier,” he jokes, slinging an arm around Eren’s shoulders.  Time is starting to do funny things, speeding up and slowing down all at once, and maybe he’s the one who needs to relax because that really can’t be normal.  But Eren’s just agreed to have sex with him and Reiner has to take a moment to pinch his leg and make sure he isn’t having the deflowering-Eren dream.  It hurts; so definitely real life, then.  The awkward silence beginning to stifle them both is probably a good indication of that, too.  Hesitance is too imperfect for the world of fantasy.

Eren stands up so quickly that Reiner goes off balance and flops over.  He’s afraid that Eren has changed his mind, but then green eyes lock onto his own, and it isn’t rejection but anticipation that Reiner sees.  “So maybe we...maybe we should go to your room, then?” says Eren, and Reiner pinches himself again.  Still awake.

“Yeah,” he says, getting to his feet.  An idea forms in his mind and a mischievous grin is all the warning that Eren gets before he’s hoisted unceremoniously over Reiner’s shoulder like a sack of potatoes.

“Jesus _fuck_ , Reiner, are you a caveman?  Put me down, you ass,” he snaps, and Reiner, cheerful as ever, just smacks him on the ass and relishes the sharp yelp it elicits.  He does honour the request once they’re safely in the bedroom, although it isn't so much putting Eren down as it is dumping him in the middle of the bedspread.  

Thankfully he’d changed the sheets two days prior, swapping out the set Bertholdt had bought (“It’s the Dancing Titan, to be honest it scares me a bit,” he’d said, sweating a little more than usual) for a much less disturbing set in plain forest green.  Eren looks incredibly offended and opens his mouth to spew more abuse at Reiner, but it dies in his throat when Reiner crawls onto the bed and looms over him with a cocky smile.

Eren looks vulnerable like this, Reiner thinks, propped back on his elbows and legs splayed haphazardly.  Eren is wearing dark blue briefs, he notes, and this more than anything makes the reality of the situation cement itself in Reiner’s mind.  He can see the faint outline of Eren’s dick through the fabric, the contrast between dark cotton and tanned legs and the way the briefs are starting to ride up and expose the slight swell of his ass.  On impulse, he puts his hands on Eren’s knees and eases his legs farther apart.  It’s ridiculous, because he’s seen Eren half-naked countless times and there’s nothing even inherently erotic about plain blue underwear but Reiner still feels like he’s going insane.

“Christ, Reiner,” says Eren, trying to kick him.  “What are you-”

“Just looking,” says Reiner innocently, with a grin that’s anything but.  He slides his hands up Eren’s thighs, rubs his thumbs over the boy’s hipbones and leans down to breathe warm air over his crotch.  Eren jolts, breath hitching, and Reiner likes the reaction so much that he takes it one step further and mouths at the clothed bulge.  He drags his tongue firmly along the length of Eren’s cock, feels the heat emanating from the brunet’s skin as the fabric grows dark with Reiner’s spit.  Eren squirms restlessly, his fingers twitching in the bedspread as Reiner teases him.

“T-this is a hell of a lot more than ju- u-uhh - just looking,” Eren mumbles.  Reiner chuckles, proud of how wrecked Eren already sounds and how hard he’d gotten just from having Reiner lick him through his briefs.  

“If you don’t like it, I’ll stop,” says Reiner.

Eren groans in an infuriated manner.  “When did I say I didn't like it?”

Reiner grins and lifts Eren’s hips in one smooth movement, leaning down to tug at the waistband of the other’s underwear with his teeth.  Eren watches him with wide eyes as they’re pulled down tantalizingly slow, revealing his erection bit by bit.  Once Eren’s cock is entirely free Reiner abandons all pretense and simply tugs the briefs off the rest of the way with one hand, tossing them unceremoniously over his shoulder.

The look on Eren’s face is priceless, torn between outrage at Reiner’s carelessness and embarrassment at being so utterly exposed.  Reiner actually has to stop him from clamping his legs back together, spreading them wider than before both to make a point and to fully appreciate the sight laid out before him.  Eren is fully erect, beads of precome leaking from the tip and onto his toned stomach, and his asshole twitches under Reiner’s needlessly prolonged gaze.  

Reiner swallows hard and lowers Eren’s hips back onto the bed.  “Take off the shirt,” he says, his voice much huskier than usual, and while Eren obliges he does the same, nearly popping the buttons off in one-handed haste.  Once it’s off, Reiner lays back against the pillows and beckons Eren over.

“You look ridiculous,” mutters Eren, trailing his fingertips hesitantly over Reiner’s chest.  He’s totally fixated on the muscular torso before him and it’s incredibly endearing.  “Do you do nothing but work out all day?  I couldn't get like this if I tried.”

Reiner laughs.  “I’m just built bigger than you, Eren, nothing to be done about it.  Don’t be jealous.”

“I’m not _jealous_ -”

“Sure you’re not.  But hey, I’m not complaining when you’re staring at me like I’m a wet dream come to life.”

Eren’s face flushes far redder than it should and he quickly averts his eyes.  “I wasn't staring,” he mumbles uncertainly, and Reiner snorts.

“Sure you weren't.  C’mere.”  Reiner’s hand cups the back of Eren’s neck and guides him down for a kiss.  He means for it to be short and chaste, something to calm Eren down in preparation for what they’re about to do, but Reiner is pleasantly surprised when a warm, wet tongue glides across the seam of his lips.  Eren is an enthusiastic kisser, if a slightly sloppy one, and their teeth end up clicking together awkwardly more than once.  But Reiner is biased, so to him it’s one of the best makeout sessions he’s ever had.  It’s only in anticipation of more intimate activities on the horizon that he can bring himself to break apart from Eren, admiring the redness of the brunet’s mouth.

“I want you to suck me off,” Reiner murmurs.

“You want me to…” Eren swallows once, clears his throat awkwardly and frowns.  “It’s not going to be good...I don’t really know how.”

Reiner actually rolls his eyes.  “That’s why we’re doing this, isn't it?  Now shut up and get over here, back towards me.  Legs on either side...yeah, perfect, now lean forward - don’t give me that look, Eren, you agreed to this - there you go.”

“This is fucking ridiculous, Reiner.”  Eren’s voice cracks with mortification at the position they’re in, his knees on either side of Reiner’s shoulders and their faces practically buried in each other’s crotches.  It’s worse for him, being entirely exposed while Reiner retains his denim-clad dignity.  “Do I really need to be like this just to give you a blowjob?”

Reiner grins and squeezes Eren’s thighs in what he hopes is a comforting manner.  The view isn't exactly spectacular if he’s being  honest - just an up-close-and-personal with Eren’s cock and balls - but it’s more of a show than he ever thought he’d get in this world or the next, so he supposes he should be thanking some sort of higher power.  He hears Eren unzip his fly and has to stop himself from bucking upwards when a small, hot hand traces the outline of his dick through his boxers.  It’s maddening, the slow pace and teasing touches, but it’s also necessary if Eren is going to take anything useful away from this experience.

When he takes Eren into his mouth, the boy’s entire body shudders at the new sensations, and Reiner’s firm hands on his thighs are the only way the blond can set the pace himself.  Reiner is careful to go slow, but it’s difficult.  He can smell his soap on Eren’s skin and taste the weird, salty bitterness of precome.  Every one of his senses has been overtaken by Eren, and it’s intoxicating.  Reiner wants Eren to enjoy this as much as he is, if not more.  He wants to make Eren his, completely his, even if only for this one day, this practice run, bad intentions couched in good ones.

So he focuses on the reactions, how Eren moans and arches his back when the head of his cock is teased, the way the muscles of his stomach tense with every gentle, deliberate scrape of a tooth.  Eren seems to like all the wet, filthy sounds Reiner makes, and he swears and whispers something that sounds suspiciously like “again” when Reiner’s tongue presses flat against his perineum.  Reiner is so fixated on getting him off that he’s caught off guard when his own dick is suddenly surrounded by the warm wetness of Eren’s mouth.

Eren is a quick study, copying Reiner’s movements as closely as he can.  Still, for all his efforts, it’s not exactly a good blowjob.  It’s not terrible either, just painfully obvious that Eren has indeed never sucked dick in his life.  He’s hesitant and sloppy, not as mindful of his teeth as Reiner would like and has no clue what to do with his hands while his mouth is occupied, but he’s trying hard.  Erotic, maybe.  Endearing, definitely.  Determination has been and always will be Eren’s defining trait.

Reiner wishes he could see Eren’s face properly, wonders if the Eren in his dreams matches up to the real one now.  He wonders how Eren’s mouth looks wrapped around his cock, if his lips are just as red and swollen as he’s imagined.  He wants to know how exactly how Eren’s hair sticks to his sex-sweaty forehead, the precise colour of the flush creeping down his skin, whether or not those stupidly bright green eyes are open or closed while he gives head.  If there is a merciful god anywhere in the world, Reiner prays that he’ll get a chance to see that sight at least once before he dies.

He bobs his head, taking Eren in deeper with every downward movement until he can feel the head pressing comfortably against the back of his throat.  If Eren tries to say something, it’s muffled by Reiner’s cock, but from the desperate attempts to roll his hips downwards it’s clear that being deepthroated is something Eren enjoys.  Reiner is glad he’s had so much practice in the past;  Eren, however, is not so lucky, and in his haste to mirror Reiner’s actions he tries to do too much too quickly.  Reiner takes pity on him as he coughs and tries to catch his breath, pulling off of Eren’s cock with one last slow lick and kissing the vein along the underside for good measure.

“Sorry,” Eren rasps, moving over to sit on the bed with his back to the blond, and Reiner doesn't have to see his face to know that he’s frowning.

“Don’t be sorry.  No one does it perfectly on their first try.”  Reiner reaches over, rubs Eren’s shoulders comfortingly and kisses the back of his neck.

“You’re really good at it,” mumbles Eren, and Reiner can’t help but laugh against his skin.  “But please say you’re gonna touch me soon, or I’m gonna have to hurt you.”

“Threatening the person you’re having sex with isn't kosher, Eren.  In case you needed it spelled out for you.”

“Getting me this hard and then not doing anything isn't _kosher_ , so for Christ’s sake get on with it, please.”  Eren turns to face him and this time the kiss is just as sloppy but more demanding, desperate even.  Reiner wishes it wouldn't end, but he needs to get the lube.

“Just relax,” says Reiner, squeezing a generous amount onto his hand.   “You trust me, right?”

Eren eyes the lube with an expression Reiner can’t exactly pin down, but it’s definitely not enthusiasm.  “I do, but…”

Reiner cuts him off with another kiss, easing Eren onto his back.  He knows that whatever he says now isn't going to do anything for Eren’s nerves, so the best thing he can do is just get on with it.  Eren winces when Reiner works a finger past the tight ring of muscle, hands twitching as if trying to decide whether or not he should try pushing Reiner off.

“You okay?  Does it hurt?”

“Yeah, I’m fine” says Eren, shifting a little.  “It doesn't hurt, just feels weird.  What genius came up with the idea to stick things there, anyway?”

It’s incredibly unsexy, but it’s also just like Eren to be so blunt, so Reiner just concentrates on the only thing that will get him to shut up - proving him wrong.  

Failed dirty talk aside, Reiner has to admit that Eren looks gorgeous laid out like this.  The furrow in his brow hasn't subsided - in fact, it only grows deeper, especially when Reiner starts to slip a second finger in alongside the first.  But it’s not the same as the grumpy expression he usually wears.  There’s something oddly sensual about it, the way those brilliant green eyes look directly at Reiner without wavering, occasionally flicking down to where the blond’s fingers are slowly stretching him open.  His cheeks are flushed a splotchy pink and his muscles twitch every time Reiner moves his fingers at a new angle.  He knows he’s found the right spot when Eren arches up off the bedspread, fists clenched and breath hitching loudly as Reiner smirks to himself.  “Oh my god, Reiner, do that again, what the _fuck_ is that-”

“Prostate.  Still think this was a bad idea?”  Reiner knows he’s being overly smug, but he can’t help it, not when Eren is rolling his hips in an attempt to get Reiner’s fingers to brush that spot one more time.  Reiner leans over him, pressing gentle kisses to his forehead and eyes and mouth to distract Eren from the third, final finger probing at his entrance.

Even as Eren kisses back, Reiner can’t help but worry.  Everything was going well, but what would happen afterwards?  He could be ruining their friendship, their entire relationship, just because he wanted to know what it was like to fuck Eren.  It’s way too late to be thinking of consequences right now - he’s got three fingers up Eren’s ass, for god’s sake - but he can’t help thinking about it all the same.

It takes him a minute before his inner turmoil is broken by the realization that Eren has been relatively quiet despite Reiner’s ministrations; considering  Eren’s personality, Reiner had been expecting a lot more vocalization.  He stops the lazy kisses along Eren’s throat to cup the brunet’s cheek in his free hand, searching Eren’s face for any sign of distress but finding nothing obvious.  Whatever the expression he’s wearing is, at least it doesn't seem to be pain.

“You’re so quiet, Eren.  Should I stop?”  He twists his fingers at a new angle and Eren’s nails dig crescents into his skin, mouth forming a perfect, silent circle.  “I can’t tell what you like and don’t like if you don’t tell me.”

“Shut up, Reiner,” hisses Eren, though it’s far too faint and breathless to be vicious.  “Like hell...I’m gonna do something embarrassing like that.”

“C’mon, Eren.  No one’s watching, if you wanna make some noise, do it.  It’s kinda sexy.”

“No.”

Reiner curls his fingers just so, hitting Eren’s prostate, and the brunet actually bites his lip hard enough to draw blood to keep from yelling out.  His whole body is trembling with the effort to stay silent, and the he shoots Reiner a look of hazy disdain at the obvious attempt to provoke him.

“You sure?” asks Reiner quietly, leaning closer.  “Because I think you’d sound perfect.  I want to hear you, Eren.  I want to know what you sound like when I’m stretching you open like this, what kind of noises you’ll make when you feel my cock fill you up for the first time.  I've already got three fingers inside you, but you want more than this, right?  You want me to drive you wild.”

Reiner wonders if maybe he’s going too far; Eren is red-faced and glowering, clearly embarrassed.  So he isn't really expecting it when Eren pulls him down for a heated kiss.

“Just fuck me, please,” Eren whispers against his mouth, and it’s so soft and pleading that Reiner can barely believe the words had come out of the boy’s mouth.  Reiner can’t oblige quickly enough, fumbling with the lube and slicking himself up.  He spreads Eren’s legs a little wider, taking a moment to appreciate the view before pushing in slowly.  Eren tenses up almost immediately as the head pushes past the tight ring of muscle, making Reiner hiss and falter.

“You've got to relax,” he says.

“You try to relax when you've got something that big up your ass,” bites out Eren.  “Just keep going, I’m fine.”  

Reiner has his doubts about how “fine” he really is, but Eren isn't going to admit otherwise.  It takes a couple of minutes of stops and starts, murmured reassurance and faint, indignant protests, but soon Reiner is buried to the hilt inside of him and both take a moment to adjust.  

He’s about to go crazy, what with being unable to move while his dick is sheathed in that tight heat and Eren clinging to him as though his life depends on it.  The rhythm of Eren’s breathing mingles with his own, and when Reiner finally starts to move with short, shallow thrusts he can feel and hear every single gasp and hitch against his neck.  Reiner’s shoulders are starting to sting from the bite of Eren’s nails every time he pushes a little deeper inside, but that’s fine.  All he cares about now is making Eren enjoy this as much as he can; and considering the look on Eren’s face, Reiner thinks he’s succeeded.

 _Come to think of it, he’d probably enjoy it more if he was actually learning something rather than just being fucked into the mattress._  He grins, and Eren yelps when Reiner suddenly changes their position, clinging to his broad shoulders when he lays back and hoists Eren onto his lap without pulling out.  Reiner rubs soothing circles onto Eren’s hips with his thumbs, trailing his fingertips upwards to ghost over the slight curve of his waist.

“It’ll be easier for you to set the pace like this,” says Reiner.  Eren nods, wincing at the stretch every time he raises and lowers himself onto Reiner’s cock.

“Christ, I’m glad you fingered me first,” Eren says, letting out a strained laugh that’s more a great exhalation of air than anything.  “This is a lot harder than I thought it would be...and don’t say it, Reiner, I swear if you make a joke right now-”

“I didn't say a word,” said Reiner cheerfully, rolling his hips ever so slightly upwards.  Eren’s nails dig into his chest - _who knew Eren would be a scratcher instead of a biter?_ he muses - and he sucks in a sharp breath.  “You’re doing great, Eren.  Just go as slow as you need, okay?  This is all about you.”

Eren nods, swallowing hard as he moves slowly up and down Reiner’s shaft.  It takes a while, but soon Eren’s breaths speed up and he grows bolder, more desperate.  He’s been maintaining eye contact with Reiner almost the whole time, and it’s incredibly, weirdly arousing.  Eren’s eyes have always been beautiful - and yes, Reiner knows it’s the biggest cliche this side of a rom-com - but they’re even more so like this, hazy with lust and completely fixated on him.  Reiner is so engrossed in taking in every detail of how Eren looks while riding him that he nearly misses the soft, short moan that escapes the brunet.  It’s an amazing sound, husky yet still high, muddled with desire.  Eren immediately clamps a hand over his mouth, looking mortified, but Reiner tugs it away.  

“Don’t,” he whispers.  “I want to hear everything.”

Eren’s self-restraint must have been wearing incredibly thin to begin with, because Reiner barely finishes his sentence before Eren starts riding him at a much faster pace than before, taking Reiner’s cock deeper and harder, letting every hitch of breath and moan and breathless plea for more escape freely.  Reiner’s grip is tight on Eren’s hips, and he can’t help but thrust upwards in time with the brunet.  It’s probably the most amazing sex he’s ever had, and that includes the first and only time he had a threesome with Bertl and Annie.

The room is getting unbearably hot, filled with desperate pants and the slap of skin on skin.  Reiner pulls Eren down for a kiss, more passionate than before.  “God, Eren, you’re perfect,” he breathes, and he tries to ignore the edge of desperation in his voice.  “Keep moving just like that.  Tell me how much you like it, Eren.”

Eren looks decidedly reluctant, but when Reiner holds him still he practically whines with need, trying to resume his movement in vain.  “I-I like it!  Dammit, Reiner, you’re great at sex, your dick feels so good, what do you want me to say?  For God’s sake, just keep fucking me, _please_ -”

“If that’s what you want.  Bet you’re wishing you’d done this sooner, huh?” asks Reiner with a cocky smile, and Eren responds by clenching tightly around his cock, making him gasp.  

“Maybe you should have offered sooner, then,” he retorts.  Reiner blinks stupidly, unable to come up with any sort of response, let alone a snarky one.  Eren grins, an expression that’s oddly sensual for someone who’s having sex for the first time in his life.  His movements become increasingly erratic so Reiner takes over, fucks up into Eren with long, deep thrusts, and both of them have lost all reservations about being loud, Eren moreso.

“I've wanted you for ages,” Reiner mumbles under his breath, unable to stop himself before realizing that Eren might hear him.  He silently thanks every higher power that might be listening when Eren seems not to notice, too focused on his impending orgasm.

“Reiner, fuck, I’m so close, more please, please, I-”

Eren comes with a strangled moan, streaks of white spattering across his chest and head thrown back in ecstasy.  He slumps over in a graceless heap on Reiner’s torso, pressing mindless kisses along his neck.  Reiner lays him onto his back, thrusting deeply into him for only a minute or so more before he comes too, _Eren_ whispered repeatedly, pleadingly, against his neck.  They lay there in a tired heap for a few minutes, trying to catch their breath.

“Ugh,” mumbles Eren, pushing Reiner away and squirming until he’s able to roll off of the bed with minimal lower body movement.  “You never told me it would be so messy.”

“I had to leave some surprises for you,” Reiner replies, looking over at him fondly.  “You could have just stayed, I’d have cleaned you up.”

“I can wipe my own ass, thanks, had lots of practice.”  

Reiner would take offense if he couldn't see the adorable flush of red creeping up to the tips of Eren’s ears; as it is, he knows he shouldn't laugh at Eren’s shaky imitation of a baby deer as he wobbles over to the bathroom, but he can’t help himself.

“Fuck you,” mumbles Eren.

“You just did, didn't you?” replies Reiner cheerfully.  Eren just closes the door on him in response, and when he comes back he flops facedown onto the bed, not even bothering to cover himself up.  Reiner gives him five seconds of peace before he starts poking at his butt.  “Don’t you wanna spoon?”

Eren just sort of mumbles in response, so Reiner drags him over to lay against him.  He’s always the one who insists on after-sex cuddling; he likes the warmth of another body against his, doesn't even mind the sweaty tangle of limbs they’re bound to become in the morning.  He presses his face against Eren’s neck, just listening to the rise and fall of their breathing.

“...So, you've wanted this for how long, exactly?”

Reiner stiffens, and not in the good way.   _Oh god, he heard me, I fucked up again, I fucked up I fucked up why did I say that I fucked up so supremely._

Eren just chuckles and presses himself back against  Reiner’s chest, and the blond finds it a little easier to breathe.  “Don’t freak.  You can buy me dinner and then tell me all about it, OK?”

**Notes for the Chapter:**

> anddddd that's a wrap.
> 
> next I'll be working on prequel one-shots for On Your Knees, For Me.

**Author's Note:**

> chapter two is when the frickle frackle happens
> 
> inspired by this kink meme prompt: http://snkkink.dreamwidth.org/2848.html?thread=3369504


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